DESCRIPTION: (Applicant's Abstract) Utilizing a longitudinal design and drawing subjects from a large ongoing study, this investigation will examine the relations between cardiovascular reactivity in infancy and social and behavioral outcomes in an at-risk group of children. In so doing, the study will examine the predictive role of cardiac reactivity (i.e., vagal tone) to specifically social stimuli in infancy to specifically social outcomes at 3-years of age. In addition, this study will investigate the role of caregiver stress and dysfunction in potentially moderating the relations between infant cardiac reactivity and 3-year outcome. To date, few if any studies have examined relations between cardiac reactivity and behavioral outcome in at-risk children. Participants will include approximately 1,000 drug-exposed children who have been observed on a regular basis from birth through three years of age. The design is longitudinal and will utilize measures from three separate domains: cardiac reactivity in infancy, 2) a cumulative index of risks present in the caregiving environment, and 3) a cumulative index of social and behavioral risk outcomes at 3-years of age. Analyses will address two main goals. First, domain-specific relations between cardiac reactivity to social and nonsocial events in infancy and social and nonsocial competence in preschool will be examined. Second, the relation of caregiving risk to social and behavioral outcomes will be examined. In particular, this second set of analyses will examine the potential interaction of cardiac reactivity and caregiving factors in predicting social and behavioral outcomes.